Chloric acid and corresponding salts, namely chlorates, especially alkali metal chlorates, are commonly used as raw materials in the pulp and paper industry, in particular in the generation of chlorine dioxide, which is used in the bleaching of pulp. Both in the chlorate manufacturing process and in the processes utilizing chlorate as a feedstock, there is a need to monitor the concentration of the chlorate ion on a periodic or, preferably, continuous basis. Numerous methods of chlorate ion determination are described in the literature (ref. 1, the references are listed at the end of the specification and their disclosures are incorporated herein by reference) but none of them can be applied for an in-situ determination of chlorate ion concentration, in particular at relatively high concentration levels characteristic for the processes related to the manufacture and applications of chlorate ions. The most commonly used method involves an ex-situ redox type multistep titration of a sample taken from a reactor, which requires pH adjustment, dilution and separation of other components of the analyte, such as chlorine dioxide, chlorine and chlorite, which may interfere with the titration method. A time delay between the moment of sampling and the end of the analysis does not permit a rapid response to process changes and, possibly, upset conditions, leading occasionally to unsafe situations.
There is a need, therefore, to develop an analytical method enabling an in-situ determination of chlorate ion concentration at the levels characteristic for processes including both the manufacture and utilization of alkali metal chlorates and chloric acid.